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Abstract

A cryogenic surgical instrument and method of manufacturing the same are described. The instrument is a cryosurgical probe having concentrically arranged cryogenic fluid supply and return tubes extending through a concentric handle portion into a closed end probe shaft wherein the handle portion and a substantial length of the probe shaft are evacuated to provide a layer of thermal insulation between the cryogenic fluid supply and return tubes and the exterior of the instrument. All the parts of the probe structure are joined by vacuum brazing method carried out in an evacuated furnace. The method involves assembling the probe parts into sub-assemblies which are vacuum brazed at a temperature of at least about 1000.degree. F. and a vacuum of at least about 1.times.10.sup.-3 Torr. The sub-assemblies are then assembled into the final probe assembly which is likewise vacuum brazed. The final vacuum brazing step simultaneously draws a vacuum within the handle portion and probe shaft through small gaps between the junctions of the sub-assemblies or via a heat sealable valve which is sealed by the brazing method thereby maintaining the vacuum within the handle and probe shaft for thermal insulation. The strength and hardness of the probe shaft may be increased by cold-working, particularly by a combination of swaging and shot-peening. Probe shafts of curved configurations may also be formed. Multiple sub-assemblies and final assemblies can be formed at the same time in a vacuum brazing furnace.

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First Claim